A) Field of the Invention
The present invention relates to an optical function device using photonic crystals, a variable wavelength optical filter and a variable wavelength light source.
B) Description of the Related Art
Tremendous recent spread of the Internet is increasing the number of channels of transmission apparatuses supporting backbone networks. It has been desired to broaden the wavelength band of wavelength division multiplexing (WDM) and shorten an interval between signal wavelengths. A laser light source for a WDM communication system now used has a plurality of juxtaposed semiconductor lasers at different oscillation wavelengths.
A variable wavelength laser light source can be structured by a combination of a laser oscillator having no wavelength selectivity and a variable wavelength optical filter. A variable wavelength optical filter can be realized by a Fabry-Perot resonator having a pair of reflection mirrors whose distance can be changed.
Related art is described in Japanese Patent Laid-open Publication No. HEI-3-286587.
A laser light source having a plurality of juxtaposed semiconductor lasers is bulky and difficult to reduce the size. A variable wavelength optical filter realized by a Fabry-Perot resonator is required to mechanically move the reflection mirror and is difficult to speed up wavelength setting.